Using adb to transfer an Android app (apk and obb files) between devices

2020-12-23

Backstory: I have a (Amazon - so FireOs technically) tablet and want to have a specific app (Lego Boost Star Wars) on that device. The app is available for download via the Google Play Store. I can install the app on my smartphone. Installing the app via the Play Store on the table requires me to install the Google Play Store app on the tablet first. There are howto’s for that; but in the case of that specific tablet it just didn’t work. And: Installing the Play Store app (and the required other Google apps) seems like a bit of an overkill for just getting one app to that device. Alternatively I could trust one of the hundreds of more or less shady online Play Store download and totally not virus transmission serivces. No thank you.

I can install the app on my smartphone.

Well … am I able to get the app “out” of my smartphone and “in” the tablet? Yes! As it turns out this was fairly easy once I knew about the correct paths. Step by step:

Preparation: Enable developer settings / mode on both devices; enable USB debugging and connect to laptop (running Linux; should work the same on Windows though) with a working adb installation.
Find the APK of the app on the phone: Use adb -t <TRANSPORT_ID_PHONE> shell to open a shell on the phone, then enter pm list packages -f | grep lego to get the location of the apk file:
```
#phone# pm list packages -f | grep lego
package:/data/app/com.lego.boost.boost-92CgdA2ln-n4V_2TXlhQTA==/base.apk=com.lego.boost.boost
package:/data/app/com.lego.boost.starwars-nNr5IayJsqUaHo9FIUU-lQ==/base.apk=com.lego.boost.starwars
```
The second line is for the app (the first is of another lego app). The syntax is:
```
package:<PATH-to-APK>=<APP-IDENTIFIER>
```
(If someone knows the correct term for APP-IDENTIFIER please let me know!)

Pull the APK from the phone to the laptop:

#laptop# adb -t <TRANSPORT_ID_PHONE> pull <PATH-to-APK> the.apk

Install the APK on the tablet:

#laptop# adb -t <TRANSPORT_ID_TABLET> install the.apk

In case of the Lego Boost Star Wars app (which is built with Unity) there is an additional OBB file (with all the data in it) which needs to be transferred. OBB files are in /storage/self/primary/Android/obb/<APP-IDENTIFIER> on my smartphone and tablet.

#laptop# adb -t <TRANSPORT_ID_PHONE> pull /storage/self/primary/Android/obb/com.lego.boost.starwars/main.10025.com.lego.boost.starwars.obb
#laptop# adb -t <TRANSPORT_ID_TABLET> shell
#tablet# mkdir /storage/self/primary/Android/obb/com.lego.boost.starwars
#tablet# exit
#laptop# adb -t <TRANSPORT_ID_TABLET> push main.10025.com.lego.boost.starwars.obb /storage/self/primary/Android/obb/com.lego.boost.starwars/

Done.

Attention: This only works because my phone and tablet are both relatively compatible architectures. Otherwise the native part of the app (remember: Unity, so there are native libraries/JNI involved) wouldn’t be able to run.